1. Field of the Invention
The present invention relates to a tiltable device, in particular to a hard disk actuator device, with roll and pitch angle active control.
2. Description of the Related Art
As is known, hard disks are the media most widely used for storing data; consequently, very large volumes of hard disks are produced, and the maximum data-storage density continues to increase from one year to the next. Hard disks are read and written using actuator devices, the general structure of which is illustrated in FIGS. 1 and 2 and is described hereinafter.
In particular, FIG. 1 shows a known actuator device 1 of rotary type, comprising a motor 2 (also referred to as “voice coil motor”) fixed to a supporting body 3, generally referred to as E-block because of its E shape in side view (see FIG. 2). The supporting body 3 has a plurality of arms 4, each of which carries a suspension 5 formed by a lamina or strip fixed in cantilever fashion. Each suspension 5 carries, at its end that is not fixed to the supporting body 3, an R/W transducer 6 for reading/writing, arranged (in operating condition) facing a surface of a hard disk 7 and able to follow the surface of the hard disk 7. For this purpose, the R/W transducer 6 (hereinafter referred to as “slider”) is fixed to a joint, called “gimbal” or “flexure” 8, generally formed by the suspension 5 and including, for example, a rectangular plate 8a, cut around three and a half sides from the suspension strip, the connection portion 8b whereof, designed for connection to the suspension 5, enables bending of the plate 8a under the weight of the slider 6.
Since the actuator device 1 is a component of an electromechanical type, it is affected by a series of problems linked to friction, contamination and mechanical stresses, which may impair proper operation thereof, in particular considering the high speed of rotation of hard disks (currently, in the region of 10000 r.p.m.).
In particular, the present invention tackles the problem of vibrations of the suspension. In fact the suspension is, together with the slider, a mechanical system provided with its own vibration modes at well-determined frequencies. Although some of these modes are of little importance for the mechanical system, there are others that may create problems because they disturb reading and writing the disk. For example, certain vibration modes cause an error, referred to as “off-track error” which causes exit of the slider 6 from the longitudinal axis of the track. During writing, this may lead to a loss of data on account of undesired erasure of the adjacent tracks.
Consequently, when the control system associated to the actuator device detects dangerous vibrations of the suspension, it inhibits reading and writing in order to enable resettling of the mechanical system (suspension and slider). This results in dead times, which are incompatible with the high speeds involved and the short data-accessing times required.